It's super expensive but I would say its worth it.  I've been skiing there since I started skiing about 8 years ago.  I've watched their park go from non existent to what I would claim as the best in Wisconsin (I've heard that from others too).
Last season they had four parks: one was mainly a railyard with two small jumps, a park with the big jumps, a beginner park, and another park with a a mix of everything.  Granite Peak added a parks staff and they are the reason that it has really been stepped up, props to them.
They have a facebook page under Granite Peak Parks and a NS account and probably a myspace too.  They are constantly asking for input, photos, and videos, and they take what people say seriously.  When kids ask for different jumps they build them, and they are constantly working to arrange the flow of the park.  Check out their Facebook page for a ton of photos and videos.
If you guys plan on coming anytime in January let me know and I will show you around!